Hello,
The only way to reset the airbag is to have the fault cleared from the MRS (multiple restraint system). Unfortunatley, you have already set the fault. To prevent a fault in the future disconnect the battery before working on the airbag system and reconnect the battery only after it is all finished and back together.
You could check with autozone and see if they can clear the code for you for free. Some parts stores might do this for free. Otherwise, the only way to clear the code is to use the dealer or a secondary repair shop. I hope they can do it at a part store for you for free.
Please accept this answer. Please let me know If I can clarify anything. Please leave a short positive comment on feedback, it would be appreciated. Thank you.
The only way to clear the faults from the module as I described above is the drive cycles over time will erase the fault. Or you can try autozone and see if they can clear the fault for free. Or you can have your dealer or garage clear the fault although there might be a half hour diag charge to perform this funcion. Unfortunately since it is a safety related system BMW does not allow easy clearing of this fault.
I hope this helps. Please accept. Thank you.
BMW Mechanic
Level 1 BMW Master Certification, 9 Years Dealer experience, Team Leader, Shop Foreman